I want to buy a Lemark X125 cd

You do not need to buy it -- the printer drivers are available from LEXMARK --- the only ones I see are either for Windows XP or Windows 2000 (since this is a fairly old printer) - but one of them might work under VISTA as well (I'd try the XP deriver first and if it does not work then try the Windows 2000 ones) ---- They can be downloaded HERE (just select the OS version in the drop down box and click on filter and it will take you to the download - download it and then try installing.